There's no doubt that the .460 outclasses the .44 mag, but Elmer Keith showed that the .44 will drop just about anything on the continent. If you're a handloader and if you don't have either, go with the .460. (I'd prefer a rifle, though, as hauling large, heavy revolvers, especially with scopes just doesn't appeal to me.)
The 6-inch 629 is still a great brush gun, but many will prefer a heavy single-action. If you can handle a .460 and don't already have a .44, and if you can afford it, the .460 clearly is the winner. But does it lie beyond the point of diminishing return?
Only you can answer that.